on the broadcast tonight from washington -- ready to strike. the u.s. prepare as military attack on syria, but tonight the house speaker tells the president to slow down. we'll take a closer look at the possible consequences of american military action. remembering the dream. 50 years after dr. king's historic speech, a huge crowd comes here to celebrate, remember and inspire the nation to finish the job. death sentence for the army psychiatrist convicted in the massacre at fort hood. and air scare. a new warning tonight about the wildfire at yosemite and what it's doing to the air people are breathing so many miles away. "nightly news" begins now.

and good evening. i'm lester holt in for brian. here in washington, talk of war and peace at the lincoln memorial where martin luther king jr. delivered his famous "i have a dream" speech 50 years ago today. president obama headlined a chorus of speakers saluting the racial justice that changed this country. a lot more on that in a few minutes. but first, the remmings in this city about a possible military attack against syria as early as this week over its use of chemical weapons. tonight the pentagon says the u.s. military is ready to attack but in an interview this evening president obama says he has not made a decision to order a military strike. and new pressure on the president. the speaker of the house is demanding he make the case for any military action against syria. we want to begin our coverage with nbc's chief foreign affairs correspondent andrea mitchell in our washington newsroom. andrea, good evening. >> reporter: good evening,

lester. diplomacy came to a dead end at the united nations when the russians again blocked any action against syria. but tonight the president faces a new political challenge as you mentioned from the republican speaker of the house, asking how a military strike serves america's national security? tonight mr. obama spoke to judy woodruff and gwen about how close he is to taking military action. >> first of all, i've not made a decision. i have gotten options from our military, and had extensive discussions with the national security team. we are consulting with our allies, with the international community, and, you know, i have no interest in any kind of open-ended conflict in syria, but we do have to make sure that when countries break international norms on weapons like chemical weapons that could threaten us, that they're held accountable. >> reporter: the president's chief partner against assad, british prime minister david cameron has called a special session of parliament tomorrow

to justify retaliating against the ve sheem. >> we have to confront something that a war crime, something that is a crime against humanity. >> reporter: despite the devastating images of dead men, women, and children that have shocked the world and u.s. claims of hard intelligence, even today a week later the syrian ambassador to the u.n. accused the rebels of gassing government troops. >> dozens of syrian soldiers are currently treated in the syrian hospitals due to this use of chemical agents by the terrorist armed groups operating in the countryside of damascus. >> reporter: the warships are ready, targets chosen, limited cruise missile strikes and the regime in command and control, but questions tonight from some experts about what a limited strike without broader strategy would accomplish for the president. >> when you're using military power you ought to know what is the political purpose you're trying to achieve.

and if it's to stop chemical attacks, a limited military strike won't do it. not only does the president have trouble with congress, but prime minister cameron has been to delay any votes because of opposition in parliament. >> all right. thanks. we heard the president talking about meeting with his national security team. that is because there are a lot of what ifs here about striking syria. the stakes are high, the consequences unknown in a region already unknown for instability. our chief foreign correspondent richard engel is live with more on the ground. good evening. >> reporter: good evening. the u.s., frankly, faces bad choices for syria due too little and it looks too notch could create even more unrest in the region. u.n. inspectors back at work today collecting blood samples, looking for evidence of chemical

weapons. a top u.n. envoy said indications are they were used, but he didn't say who did it. >> some kind of substance was used that killed a lot of people. some people say 300, maybe 1,000, maybe more than 1,000. but this isn't acceptable, this is outrageous. >> reporter: the u.s. want to continue inspections saying it's necessary before military action, but syrians aren't counting on the u.s. listening. the wall street journal's sam dagger is in damascus tonight. >> on the serves, everything is normal. check it points are normal, around the city, the city center is firmly controlled by the government, and the government forces. >> reporter: but there are fears the already-simmering middle east could boil. what could follow if the u.s. strikes? how will syria's allies respond? iran backs syria. so does hezbollah and lebanon,

iraq and russia. iran and hezbollah both have missiles that can hit israel. israel put its missile defense system on high alert, deployed more troops near the syrian border and called up reservists as israelis lined up for gas masks. what happens if assad falls? a lot depends on how far the u.s. goes. big strikes and the syrian regime could collapse leaving rebels including a growing number to al qaeda to fight for control. assad, desperate, could even use more kem cap weapons. and what happens if the strikes have no impact? assad stays in power and there would be little justice for this man, reunited with his son missing since the gas attacks. presumed dead like his brothers or the still unidentified children like baby number 14 on a poster at at clinic outside

damascus. many syrians don't what the regime to just get a slap on the wrist. lester? >> richard engel tonight, thank you. now as promised, why we're here in washington today. 50 years ago today a quarter of a million people marched on the streets of washington in a protest for racial, social, and economic justice. it was a day that challenged this nation's conscience. from the steps of the lincoln memorial, a 34-year-old martin luther king jr. spoke forcefully and passionately and found the words that would define the struggle "i have a dream. today a new generation gathered here to renew that dream, including the country's first african-american president. it was a day of memories revisited, and hopes renewed. [ chanting ] >> reporter: thousands gathered in the light rain to mark the day a half century ago when america's civil rights movement took center stage and the reverend martin luther king jr. made history.

>> i have a dream today. [ cheers ] >> reporter: even king might not have dreamed 50 years later a black president would follow in his footsteps. >> because they marched, city councils changed and state legislatures changed and congress changed and yes, eventually the white house changed. >> reporter: today's marchers followed the route taken in 1963. all colors, all ages. they crowded onto the washington mall under the gaze of abraham lincoln and of king himself. immortalized in stone between the lincoln and jefferson memorials. some were here 50 years ago. edith lee payne captured in this iconic photo reunited with photographer roland sherman. lori brenner and dwight flowers who later married both marched. >> it gave me a tremendous amount of hope. >> reporter: in 1963, gordon gunderson was a park ranger on the podium with dr. king. >> it was the most beautiful poetry you would ever want to hear.

♪ it's about justice, it's about freedom ♪ >> reporter: peter, paul and mary 50 years ago, and today without mary, but with the parents of trayvon martin and newtown father mark barden. 23-year-old activist john lewis -- >> we must wake up america. >> reporter: -- now a congressman and elder statesman. >> we must keep the faith and keep our eyes on the prize. >> reporter: the day was a celebration and call to action, without the fears that shadowed the 1963 march. civil rights leader medgar evers had been assassinated just weeks before. the birmingham church bombing killed four young girls just weeks later. today evers' widow spoke. >> freedom is not free. >> reporter: and the bell onstage, it was rescued from that birmingham church, and rung today by members of the king family. >> so we come once again to let freedom ring.

>> when we allow freedom to ring, when we let it ring from -- >> reporter: king's words reached future presidents. >> they opened minds, they melted hearts, and they moved millions including a 17-year-old boy watching alone in his home in arkansas. >> reporter: president johnson who was represented by daughter lynda. president kennedy by daughter caroline. >> 50 years ago my father watched from the white house as dr. king and thousands of others recommitted america to our highest ideals. >> reporter: on that day, reverend king and others met with kennedy at the white house. >> the president made it very clear that we would need very strong bipartisan support if we were to get a civil rights legislation this year. >> reporter: today the president stood where king stood. >> we might not face the same dangers at 1963, the urgency

of now remains. no one can match king's brilliance, but the same flame that lit the heart of all who were willing to take the first step for justice, i know that flame remains. >> we'll be able to join hands and sing in the words of the old negro spiritual, free at last, free at last, thank god almighty we are free at last. >> reporter: king would never guess 50 years later his bust would proudly be displayed in the oval office, but it's there along with a framed copy of the original program of the march on washington. a reminder it's not too late to be part of our nbc news dream day project. we asked viewers along with political figures, leaders and celebrities to tweet us their dreams and send us their dream videos. nbcnews.com/dreamday, and you can send your dreams on twitter

using the #dreamday. in texas tonight, the death penalty for nidal hasan. former army psychiatrist who went on a deadly rampage at fort hood nearly four years ago, an attack that's been called the deadliest act of terrorism on american soil since 9/11. mark potter has been covering the trial and reports tonight from texas. >> reporter: it took nearly four years after the fort hood shooting rampage in which 13 were killed, and 31 wounded for nidal hasan, the convicted gunman to be convicted and sentenced to die. the panel ordered he be dismissed of the army and stripped of his pay. the decisions were unanimous as the sentence was read, hasan looked at the jury and judge, but had no apparent reactions. those would come from the victims' families who spoke after the sentencing. joe lean cahill lost her husband michael cahill when he was shot

trying to stop hasan's attack. >> today a weight has been lifted off of my shoulder. he has been held accountable for his actions, and the panel gave him justice. >> reporter: in arguing for the death sentence the prosecutor, colonel michael mulligan set up hasan an army psychiatrist, he was trained as a doctor to save lives. on 5 november he only dealt death. in the beginning of the trial hasan said he was at gunman. mulligan argued he not now and will never be a martyr. he is a criminal. a cold-blooded murderer. gayle hunt who lost her son army specialist j.d. hunt in the shootout agrees. >> anyone who would use their religion to commit acts of terrorism serves no god except their own hatred and self-interest. in wrapping up his arguments, saying you should not punish him for his religion. you should punish him for hit hate. when asked if he would address

the jury, hasan who acted as his own attorney said simply, i have no closing statement. now, officials say hasan will be transferred to the military prison at fort leavenworth, kansas, where he will likely spend years waiting out the more -- automatic appeals. >> mark potter, thank you. still ahead, the fire in yosemite and the growing concerns it's making the air dangerous to breathe as much as 100 miles away.

tonight fire crews battling one of the largest fires in the history of california say it will likely be weeks before the fire is contained and new concerns tonight about the smoke from this massive fire. nbc's miguel almaguer has more tonight. >> reporter: the firefight on the front lines of the rim fire may not be over until winter. while there's steady progress in the push for containment. >> look at those flames just ripping across those trees.

>> reporter: tonight growing concern far away from the fast-moving flames. at the hetch hetchy reservoir, the city of san francisco's pristine water supply, there's no letup in the ash raining down. scientists are checking water quality for the 2.6 million who get their drinking water from here. but it's rain that gives them cause for concern. >> the greatest risk of this fire is an enhanced input of sediment, which is essentially dirt from the forest floor in to the reservoirs. >> reporter: where there's ash there's also smoke. this column shooting 30,000 feet into the air. for hundreds of miles in both directions, we just have smoke, ash, and flames. downwind in reno, nevada, 100 miles from the flames, bad air is forcing schools to cancel all outdoor activities. back near the blaze -- >> it's making my throat very, very dry and scratchy. >> reporter: dozens have been hospitalized, all others warned to stay indoors.

>> there's definitely a higher risk of developing respiratory infections with all of the particulate matter in the air. >> reporter: the smoke in this region could linger for months. with more than 280 square miles charred so far, firefighters are using new technology to survey the damage. drones like this one identify hot spots as fire reshapes the landscape, giving this region a new look and new worries. tonight this fire has destroyed some 31 homes. it threatens 4,500 structures, it is just over 20% contained. lester? >> all right, miguel. thanks for the update from there. up next, as we continue from the nation's capital, where are the worst drivers on the american road? there's a new list out tonight.

looks like a star is born after a giant upset by an american teenager at the u.s. open.

17-year-old victoria duvall ranked 296th in the world shocked former u.s. open champion samantha stosur in the first round last night under the lights of arthur asch stadium in new york. duval plays her next match tomorrow but later today talked to nbc news about her big win. see the interview tomorrow morning on "today." though a lot of folks would beg to differ, a new report says washington, d.c. has the worst drivers of any big city in america. the nation's capital takes the bottom spot in allstate's annual survey for the sixth year in a row. the insurance giant says washingtonians get in an accident about once every five years. drivers in ft. collins, colorado, are the safest. we put the full list on our website to see where your city ranks. i may walk back to the airport tonight. and the mission still classified tonight in the sky over southern california. the national reconnaissance office launched a massive rocket

into orbit carrying a u.s. spy satellite from vanderburgh air force base. air force security and police shut down a nearby beach as a precaution, but everything went off without a hitch and the u.s. now that a new pair of eyes in the sky. there's more to tell you when we come back. we're with some of the people who came here 50 years ago, and came back here today with dreams of their own. ♪ we shall overcome

>> now is your chance to share your dream. we're back with a live look at the nbc news dream project on display at the crossroads of the world's times square in new york city. all day your tweets have been streaming in using the #dreamday. so many completing the sentence, i have a dream that -- and all week we've spoken with some of the thousands who made the trip here to the national mall to take part in the anniversary of dr. king's dream, telling us their stories, including some who were there to hear it in person 50 years ago. >> that's your bus. right there. >> uh-huh. >> okay. >> do i have anything?

>> my grandmother told me, she said, guess what. martin luther king will be in town. and we've got to go see him. i said, oh, yes. so we walked to the mall. we didn't live far. and that's where we was amongst a throng of people. ♪ i'll be buried in my grave >> my name is florence lawton, and i am from decatur, georgia. i just never dreamed that i would see this day come in my lifetime, and i want to be a participant. >> we made it. we're here. 50 years ago! >> 50 years ago, two other guys and myself were the first three people to arrive here. we hitchhiked from gaston, alabama, and it was our job to

put together all of those professional signs that you see. my name is robert abel, and 50 years ago i was here for the march on washington. i'm sure i touched every last one of those signs. ♪ his truth is marching on ♪ amen >> i have a dream. >> i have a dream. >> i have a dream. >> i have a dream that we will stop focusing on material things and start loving and caring for each other. >> i have a dream that one day we won't be judged due to our sexual orientation or race. but realize that's what makes us all beautiful and different. >> when i was here 50 years ago, in the v.i.p. section, i was honored to have a ticket. then to hear martin luther king lay out the dream to give a moral foundation to the movement, it was unbelievable. >> you'll make it the next one? the next 25? right. >> how about that. >> i have a dream that one day this world will come together as one. oh, what a wonderful world this

world would be. >> an inspiring and emotional day here in the nation's capital. that's our broadcast for this wednesday night from the washington mall. thank you for being with us, everyone. i'm lester holt in for brian. we hope to see you here tomorrow. good night. right now at 6:00, get a good look. it is almost closing time. a live look at the bay bridge. it will be closed to traffic in just two hours. commuters and transit agencies are gearing up for the big shutdown. >> we are counting down to the longest shut down of the bay bridge since 1989 after the earthquake. one of the primary arteries of the bay area will be closed for the next five days. when the new eastern span opens

this is what it will look like to drivers. it's set to open next tuesday morning, the day after labor day. cheryl hurd joins us from the toll plaza. we were here 24 years ago when this all began. hard to believe it is about to be completed. >> 24 years ago i think i was 2. just kidding. this is ground zero for the closure project and to my right they are full of live trucks and reporters. and later this evening we will find out what will happen later on this evening. but as you can see traffic is rolling smoothly. caltrans is hoping to get the last car across the bridge by 8:00 p.m. >> i will be on the b.a.r.t. i imagine it will be rough. >> that's how bay area commuters are feeling hours before the bridge shutdown that starts at